Transparent thermal insulation



May 20, 1947. c. H. HERTER 2,420,879

TRANS PARENT THERMAL INS ULATI 0N Filed Dec. 1, 1942 3 Sheets-Sheet l INVENTOR Charles ff. iierel' ATTORNEY MayZO, 1947. H, HERTER 2,420,879

TRANSPARENT THERMAL INSULATION Filed Dec. 1, 1942 3 Sheets-Sheet 2 INVENTOR ,.i 4 Charle; ,H. .Herter ATTORNEY Mi W9 May 20, 1947. c. H. HERTER TRANSPARENT THERMAL INSULATION Filed Dec. 1, 1942 3 Sheets-Sheet 3 1 INVENTOR v 1 Charles H. Herter Patented, May 20, 1947 l a I 2,420,879

UNITED STATES PATENT OFFICE 2,420,879 TRANSPARENT THERMAL INSULATION Charles H. Herter, New York, N. Y.

Application December 1,1942, Serial No. 467,484

4 Claims.

This invention relates to heat insulation and more in particular to a heat insulated window construction of a type for use in a fiat-top, selfservice refrigerator display cabinet.

An object of this invention isto provide an insulated window which will transmit light, but

which will prevent the passage therethrough of any substantial amount of heat. A further object is to provide a window construction of the above character which is suitable for use in a refrigerator cabinet where products such as packaged frozen food, are stored, displayed, and easily removed. A further object is to provide a refrigerator cabinet having doors incorporating'therein a window construction of the above character. A still further object is to provide a self-service cabinet which may be opened with one hand, and which may be easily closed after the product has been removed. Another object is to provide a heat-insulating, transparent structure. A still further object is to provide apparatus of the above character which is sturdy of construction, economical to build and operate, and which will give satisfactory results under varying conditions of use. Other objects will be in part obvious, and in part pointed out below.

The invention accordingly consists in the fea-- tures of construction, combinations of elements, and arrangements of parts as will be exemplified in the structure to be hereinafter described and the scope of the application of which will be indicated in the following claims".

In the drawings:

Figurel is a perspective view of a refrigerator cabinet constituting one embodiment of the invention;

. Figure 2 is a sectional view of another embodiment of the invention partially diagrammatic to show the distribution of, the temperature drop in a window construction;

Figure 3 .is an enlarged sectional view of the cabinet of Figured; and,

Figure 4 is a sectional view on the line 4-4 cabinets have been used for frozen foods, the cost of operation has been excessive, with the result that the distribution costs have been high. In addition to this, the foods have been constantly I subjected to the' possibility of premature thawdistribution. It is an object of this invention to provide a display cabinet for frozen foods which will reliably maintain the foods at a safe temperature while, at the same time, the foods will be displayed and will be easily accessible. These and other highly desirable results are obtained without excessive cost. I

In the illustrative embodiment of this invention, the foods are stored in a flat-top display cabinet having horizontally sliding doors or lids. Packaged frozen foods are carried within the cabinet upon vertically movable trays or elevators, and these trays are properly positioned at all times so that the top packages upon each tray are held adjacent the lids. The cabinet is of the self-service type, and the customer may open the cabinet by pulling the lid outwardly, and may then remove one or more packages of the food and reclose the lid by merely pushing it inwardly. By providing a horizontal opening in the top of the cabinet, the heavy cold air tends to remain in the cabinet even though the lid is open, and as a result, a very small amount of warm air enters the cabinet. Furthermore, when the cabinet is partially filled, most of the air space below the packages, and the packages themselves form a cover or lid for this air space when the sliding lid is open. In this manner, the cold air within the cabinet is protected and is not replaced by warm air. This materially reduces the possibility of the temperature within the cabinet rising to a point where the food will be partially thawed.

Furthermore, when warm air enters the cabinet, it carries with it a large amount of moisture,

and when this air is cooled, this moisture condenses and forms frost upon the refrigerating surfaces. The forming of frost in cabinets of this character is a very serious problem, as the frost insulates the refrigerating surface, and in maintaining the proper cabinet temperature, an extra load is placed upon the refrigerating equipment. Such a coating of frost may even cause the temperature within the cabinet to rise to a point where the food will be damaged. It is thus seen that by preventing the entry of warm air into the cabinet, many of the difficulties normally encountered during operation are materially reduced. and the products are maintained in proper condition.

In this embodiment. the top wall of the cabinet is provided with horizontal windows through which the contents of the cabinet may be readily seen. These windows are in the form of sliding lids, each of which covers an opening through which access may be had to the cabinet. Each of these lids is in the form of a frame which holds a large number'of closely spaced. parallel sheets of transparent material. These sheets divide' the space within the frame into a number of horizontal sheet-like dead-air spaces, and due to the fact that the air spaces are thin and are positioned horizontally, they provide an excelheat is transmitted by three different actions, that is, by conduction directly through a substance, by radiation directly through a transparent substance, and by convection through gas-filled spaces in which the gas, such as air, is heated and rises from or along awarm surface to replace cooler and heavier air. With the present type of window, conduction is very small as heat is not readily transferred in this manner through'either the transparent insulating material or the air. Likewise, radiation is small as the normal light radiatesvery little heat.

Furthermore, convection is largely eliminated as the basic conditions necessary for convection that convection'is largely eliminated by making around the inner side walls of the cabinet (see Figures 3 and 4) indicated at 6. and will be discussed more in detail below Referring particularly to Figure 3, cabinet 2 is formed by an outer metallic shell 8 and an iner metallic shell 10, and these two shells are spaced apart with the space therebetween filled by a rigid insulating material I 2, illustratively compressed cork-board. The top edges of the shells are joined at the top by a. strip l3 of heatinsulating composition board so that the space occupied by the insulating material is effectively sealed and the inner shell is insulated from the outer shell. The cabinet is supported at each corner (Figure 1) by four legs l4, there being h one leg at each corner.

The top wall of the cabinet is in the form of a frame which carries eight sliding lids it, with I four lids upon each side of the cabinet, and in walls of the inner shell, and the coiled pipe unit these air spaces of a thickness of three-eighths of an inch or less. With an air space of this thickness, the air throughout the space is elf-1 fectively stratifled, so that the warm film of air covers the top wall and the cooler film of air covers the bottom wall. In this manner, a transparent insulating medium is provided which maintains heat transfer at a minimum and also avoids the difficulties encountered in providing a vacuum chamber.

The present invention relates to transparent thermal insulation of the character which can be applied in a variety of different structures. Certain=of the advantages of the invention are associated with a, horizontally extending window structure, although many of the advantages are of a general nature and can be obtained when the invention is applied to a vertically extending 6 extends through these recesses. The coiled pipe-unit and the liner form a heat-transfer unit whereby the heat is effectively withdrawn from 'the cabinet, and by providing this construction,

the unit is sturdy and cooperates with the shell structure to form a sturdy cabinet. At each end, this heat-exchange unit is provided with two vertically extending strap members 22, and .spaced along each side of the cabinet are four similar strap members 23. Each strap member 23 is reinforced at. its top by a metallic block 24 and is held thereto by a screw 25, shown best in Figure 4. Block 24 fills the space between the top of 1 1 the strap member and the wall of the inner shell and extends along the adjacent top portion of window or door. Thus, for example, the window structure is admirably suited for use in vehicles such as trains and aeroplanes where light-weight,

heat-insulating panels are desirable.

Passing now to a more detailed discussion of the present embodiment and the specific details tray 40 having a flat bottom and upturned side the drawings with the cabinet indicated at 2, and

a refrigerating unit indicated at 4. This refrigthe liner 20. Each strap 22 is attached to a similar block 21 by a screw 23. v

The interior of cabinet 2 is divided into four compartments by means of four guard frames or baskets 26 which are removably positioned transversely within the cabinet. The construction of baskets 26 is best shown in Figures 3 and 4, there being at the bottom a rectangular frame 28 and at the top a similar rectangular frame 30, and extending between these frames are vertical bars 32. The bottom of the basket is formed'by three cross straps 34 which are equally spaced and extend transversely of frame 28. Extending across the top of each basket at the center is a brace strap 35. At the center of each end of the basket are two vertical straps 38 (Figure 4) which are spaced apart to provide a vertical slot 38 to be referred to :below.

Positioned within each of baskets '26 is a and end walls, which is supported at its ends by a pair of angle brackets 42. Each of angle brackets 42 has one side welded to the central lower portion of the end wall of the tray, and the other portion of the angle brackets extends through the adjacent slot 38 between straps 38. Bracket 42 is removably attached to a supporting cord 44 which is held by a clamp 43 and which extends upwardly with its upper end coiled about and attached to a large sheave 48 of a pulley generally referred to at 48.

I do

Pulley 48 is supported ,on block 24 by a stud bolt 50 which has a bearing portion 52 which fits against strap member 23 and assists in holding the strap member in place. Pulley 48 is provided with a small sheave 54 about which is coiled a cord 56 with the end of the cord attached to the sheave. The other end of cord 56 extends downaaaaare of the cabinet and over the top of each lid is a top board 82 which braces the lid-supporting structure. In use, a, lid may be pulled out with one hand, and after a package has been removed the lid'may be pushed shut by either the hand orthe body. Thus, the act of removing a packa e may be a one-hand operation.

the top of the cabinet, and as packages are piled onto the tray, the tensionon the springs 60 is gradually increased so that the springs are stretched out and the tray moves downwardly.

The tension of springs 60 and the ratio between the sizes of the two sheaves of the pulleys 4i! are so adjusted that the weight of one layer of pack ages moves the tray downwardly the thickness of the layer of packages.

Thus, the top layer of packages is always at the top of the cabinet. The initial adjustment of the tension of each of springs 60 is obtained by adjusting the lengths 'of cords 44 and 56. Each of cords 56 is adjusted at its buckle 58, and each of cords 44 is adjusted by pulling the end of the cord downwardly through its bracket 42 and putting clamp 43 in place. Such an adjustment is normally suflicient even under varying conditions, but when conditions change sufliciently, readjustment is not difllcult.

As indicated above, the top of the cabinet is formed mainly by eight windows in the, form of lids l6, and these lids are carried by a frame structure which is removably attached to the top of the side walls. This frame structure comprises a longitudinal frame member. 84, a transverse end frame member 66 at each end, and three intermediate tran'sverse frame members 68. As shown best in Figure 4, transverse frame members 00 extend over the side edges of'the baskets 2B, and one of the lids on each side of the cabinet is over each of the baskets. Thus, the products within each compartment maybe viewed through a window and removed throughan opening on either side of the cabinet.

Each of lids l8 isformed by a frame of moulded material which rigidly holds a number of sheets of transparent insulating material. Each of the side walls 88 of the frame is provided with an angular side face 90, and as shown in Figure 3,

the end of the frame which is at the center of wardly away from the center ofthe cabinet. Ac-' eordingly. each of frame members 68 is provided In this embodiment, the transparent insulating material carried by the lids is in the form of a thick pane of glass 08 at the top, a thin pane 98 at the bottom and a number of sheets of Cellophane I00 equally spaced between the two panes.

The panes and the Cellophane are rigidly held at their edges and are positioned so that the air space between the two panes is divided into seven thin layers of equal thickness, each air space being approximately three-eighths of an inch thick. As has been pointed out, above, it has been found that by providing horizontal air spaces of substantially the thickness disclosed, the entire fbodyof .air in each space becomes stratified,

thereby forming an excellent heat-insulating medium.

with a top board 10 and a. brace 12 which is narraw at the top and which flares outwardly toward the bottom with two angular side faces 14, and each of end frames 80 is provided with a similar top board 16 and a brace member 18 which has an angular side face 80. Longitudinal frame 64 is similarly constructed with a top board 82 and a brace member 84 having angular side faces 86.

Thua'eachlid is mainly supported on the angular faces so that the weight of the lid aids in maintaining a heat-tight seal around the'lid. As

shown best in Figure 1, extending along-the edge The lower pane 98 is of Lucite which is a synthetic composition which is transparent and rigid, and which has low heat absorbing ability. Thus.

pane 98 provides excellent heat insulation, and when the lid is pulled out and the pane is exposed to the warm air, it will not become fogged. The upperpane 96 is of glass and thus will not be scratched or damaged during normal use.

Referring to Figure 3, at the upper left-hand edge of the cabinet, a vertically sliding stop 94 is provided (see also Figure 4) which normally extends upwardly beyond the lower edge of the lid frame to a point adjacent the pane 88. Thus, as the lid slides outwardly, the stopprevents movement of the lid beyond the edge of the opening.

Stop 84 may be slid downwardly away from the 11d when the lid is to be removed.

In this embodiment, provision is made to light the interior of the cabinet without placing an undue load upon therefrigerating equipment. Accordingly, as shown in Figure 3, the bottom of longitudinal frame 64 is provided with an upwardly extending trough or channel I02, and positioned beneath this channel are suitable tubular fluorescent lights I04. The top frame 30 of each basket 26 is cut away on its two sides at- I06 so that one light tube may extend over two baskets. The surfaces of channel I02 provide a reflector for the light and straps 35 protect the light from being hit by packages or otherwise injured. In addition to this, straps 35 act as stops to prevent the trays from moving a package against the light if the packages should become piled in the center of a tray. Furthermore, if for any reason the springs holding a tray should be out of adjustment, the strap 35 extending over the particular basket would prevent the springs from lifting the packages against the lids.

Extending throughout the length of longi: tudlnal frame 64 is an illuminated signboard indicated at I08. This slgnboard includes five triangular brackets H0 which carry at the top a reflector H2 into which are mounted suitable tubular lights I. Mounted upon these brackets above each'lid are four removable strips H6 and a similar but larger strip H8. ,These strips bear notations listing the products which may be had by opening that particular lid, with strip I I8 bearing the type of product such as vegetables, meat, fish," etc., and each of the smaller strips H6, bearing the name of a particular 8 of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbe- .fore set forth, or shown in the accompanying drawings, is to be interpreted as illustrative and not in a limiting sense.

I claim: 1. In refrigeration apparatus of the character "described, the combination of: a cabinet having of a square helix, and at each corner, the pipe unit is bulged outwardly and rounded to permit the pipe unit to expand and contract with changes in temperature.

In the embodiment of Figure 2, a transparent thermal insulation construction is provided wherein two spaced panes of glass IBGeand I98 have therebetween seven sheets of Cellophane 200, which are the same as sheets I00 in the embodiment of Figures 1, 3, and 4. The frame in Figure 2 is shown in the background of theflgure, and is the same structur as in the other illustrative embodiment of the invention. The seven sheets 200 divide the space between the panes into eight equal dead-air spaces of 1"; inch thickness. Figure 2 has a diagrammatic representation of an actual insulation of this window structure mounted in a vertical wall with atemperature at the left of 90 F., and'a temperture at the right of 0 F. Under these illustrative conditions, there is a 9 drop across each of the dead-air spaces, and the heat loss through the insulating window is 12.42 B. t. u. per square foot of area per hour.

With this construction, the temperature drop between the adjacent spaces is sufiiciently small to prevent fog ing or condensation of moisture within the spaces even under the most extreme conditions of use. Both of the panes are capable of withstanding wear without danger of scratching so that this window may be used ina door or in a vehicle where both sides of the window are constantly subjected to wear and abuse. The sheets of Cellophane are held taut, and the deadair spaces are closed so that air does not circulate as when ventilation holes are provided. Even if there is leakage at the edges of the dead-air spaces, a good insulating effect is still obtained,

and the presence of water vapor does not me.- terially-interfere with the usefulness of the transparent thermal insulation as fogging and condensation are avoided.

It will thus be seen that I have provided a practical and efficient apparatus for accomplishing the several objects hereinabove mentioned as well as many others in a successful manner. It has been found that this thermal insulation has insulating qualities which are equal or superior to those of an equal thickness of pure corkboard. Thus, a light-weight, transparent insulation is provided which approaches the optimum. In the illustrative embodiments referred to above, the spacing of the insulating members of such as to provide dead-air spaces of three-eighths inch and five-sixteenth inch, respectively. Under some circumstances, it is desirable to provide very thin dead-air spaces; thus, for example when an extremely thin window is desired, the spacing may' As many possible embodiments may be made a horizontal top opening; and a horizontally slidable door means providing a removable closure for said opening comprising, a frame of insulating material extending around the edge of said opening, and a plurality of sheets of transparent material within said frame including a pane of glass forming the surface which is the outer surface of the door means when the door means is in position to close said opening and a pane of synthetic resin having a lower thermal capacity than glass which is the inner surface of said door means when said door means is in position to close said opening.

2. In refrigeration apparatus of the character described, the combination with: a flat-topped cabinet having a top horizontal, opening adjacent one side of the cabinet and having the sides of the opening away from said side of the cabinet defined by wall portions which converge in a downward direction whereby the opening is provided with a rim with slanting upper surfaces which are adapted to slidably support a door means of, a horizontally slidable door means providing a closure for said opening comprising, a rigid frame construction adapted to be positioned within and snugly fit said opening and presenting surfaces which converge in a downward direction corresponding to the similar surfaces about said opening, said frame having a central space, and a plurality of sheets of transparent material rigidly held by said frame in parallel relationship within said central space, said sheets including a top sheet of glass and a bottom sheet of plastic insulating material having a low mean thermal capacity. I

3. In a refrigerator cabinet, a substantially horizontal top wall providing a heat insulating transparent closure comprising, a fixed frame having formed therein a rectangular opening with the frame extendingalong three sides of the opening and with the frame open along the other side, the side walls of said opening converging downwardly whereby the opening is bounded on three sides by a rim with slanting upper surfaces which are adapted to provide a support for a sliding closure, and a sliding closure positioned within said opening and supported by said rim and presenting surfaces mating with the slanting uprests upon said slanting upper surfaces with its own weight assisting in forming a wedge seal and whereby the closure may slide on two opposite slanting surfaces to permit access through the opening, said closure having a heat insulated transparent window therein which is provided with an upper surface of glass which is not easily. damaged and is provided with a lower surface of transparent Lucite having a low mean thermal capacity. 7

4. In refrigeration apparatus of the character described, the combination of z a flat-topped cabinet having a top horizontal opening adjacent one of its vertical sides; and a horizontal slidable door means providing a removable closure for said opening comprising, a rigid frame construction adapted to be positioned within and snugly fit said opening and to slide away from said opening beyond said vertical wall, and a plurality of sheets of transparent material rigidly mounted within said frame construction in parallel spaced relationship, said sheets including a top sheet of hard transparent material and a bottom sheet of a plastic insulating material having a low mean thermal capacity which is substantially less than the corresponding characteristic of glass.

CHARLES H. HERTER.

REFERENCES CITED The following references are of record in the file of this patent:

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